Mark Shand, 62, was in a critical condition after slipping while lighting a cigarette outside an after show party for a charity fund raising event.

He was rushed to a hospital suffering a serious head injury and placed on a life support machine.

However, it has now been confirmed that he later died following the fall outside the Diamond Horseshoe club.

A Clarence House spokesman said: "It is with deep sadness that we have to confirm that The Duchess of Cornwall's brother, Mark Shand, has today passed away"

The tragic news about the accident was passed to his distraught sister Camilla as she prepares for a high-profile tour to Canada with Prince Charles.

A source said earlier: “The Duchess of Cornwall and her family fear the worst after being of the accident. They have been told to brace themselves as the next few hours are critical.

“He had just stepped outside of the party and lit a cigarette when he slipped and smashed his head on the pavement. The ambulance was there quickly but it is now touch and go.”

Jon Furniss/WireImage

The travel writer and auctioneer had been attending an auction held at Sotheby’s in New York in aid of a charity helping underprivileged children and the Elephant Family - a charity which aims to save the endangered Asian elephant from extinction in the wild.

It was the climax of the month-long Big Egg Hunt NYC by Faberge which saw egg sculptures sold to the highest bidder.

A Clarence House spokesman said: “The Duchess of Cornwall’s brother, Mark Shand, has been taken to a New York hospital after falling and sustaining a serious head injury. The Duchess, her family and The Prince of Wales are clearly deeply concerned and are being kept closely informed.”

Mark recently denied being in a relationship with Strictly Come Dancing star Nancy Dell’Olio, the former girlfriend of ex-England football manager Sven Goran Eriksson.

Getty/Indigo

He described her as a “remarkable character”, but said: “Let me be clear, I have never had an affair with Nancy Dell’Olio.

“We have never dated. There is no romance; there has not been any romance, there never will be.”

He continued: “I am more likely to have an affair with a ripe pomegranate! And I am very fond of pomegranates.”

He insisted their relationship was purely professional.

“I know Nancy through my charity work,” he said.

“We have met and talked, even had a cup of tea together.

“There have been some staggering stories written which are laughably untrue.”